The basic operation and structure of a land mobile radio system is well known. Land mobile radio systems typically comprise one or more radio communication units and one or more repeaters that transceive information via the RG communications channels. These communications channels are typically narrow band frequency modulated channels. Further, trunked communication systems are organized so that a group of users are served by a set of repeaters that support trunked communication resources within an RF coverage area.
When a subscriber unit leaves the RF coverage area of one communication system, another communication system may therefore provide necessary service. A well known technique for establishing a link between two users served by different communication systems is by means of a telephone interconnect call. In order to place a call, dual-tone multiple-frequency signalling is often used. This technique is cumbersome in the dispatch environment because it requires several seconds of delay to establish the connection, as compared with the conversation which itself may only last a few seconds.
Another method of interconnecting communication systems relies upon dedicated lines that link the communication systems continuously. These lines may be either analog or digital lines that are leased from a public utility, or that are privately owned. In a dispatch environment traffic is characterized by extreme burstiness with very low average utilization. Nevertheless, the infrastructure guarantees service to worst case traffic rather than average traffic. As a result, most of the time the infrastructure remains idle. Therefore, this method eliminates an initial connection delay, but only at the expense of maintaining connection for significant periods of time when not in use.
A third method of interconnecting communication systems is by means of a packet data network. This method provides an efficient method for intercommunication system communication; however, the transmission delay can be several seconds long, making this unacceptable for voice communication.
Therefore, current methods of interconnecting communication system sites are inefficient, cumbersome to use, and do not allow an integrated solution.